1. Field of the Invention
The invention described herein is primarily for use with a cochlear prosthesis, or implantable hearing prosthesis system, or bionic ear. That is, a system of components designed with the object of restoring some sensations of hearing to the profoundly deaf. The main object of such a system is to improve speech communication, but the importance of awareness of environmental sound is also a factor to be considered.
2. Prior Art
There has been extensive activity in efforts to provide useful hearing through electrical stimulation of auditory nerve fibers, using electrodes placed inside or adjacent to some part of the cochlear structure. Systems using a single pair of electrodes have been proposed in U.S. Pat. Nos. 3,751,605, Michelson and 3,752,939, Bartz. In each of these systems an external speech processing units converts the acoustic input into a signal suitable for transmission through the skin to an implanted receiver/stimulator unit. These devices apply a continuously varying stimulus to the pair of electrodes, stimulating at least part of the population of auditory nerve fibers, and thus producing a hearing sensation.
An alternative approach has been to utilize the tonotopic organization of the cochlea to stimulate groups of nerve fibers depending on the frequency spectrum of the acoustic signal. Systems using this technique are shown in U.S. Pat. Nos. 4,207,441, Ricard; 3,449,753, Doyle; and 4,063,048, Kissiah.